Idris Khan is an artist whose focus is almost always on the colour black and shades of grey. We're most familiar with his densely sketched representational depictions of buildings such as St. Paul's but this exhibition features his latest abstract works.

At first all his works appear to be black geometric or amorphous shapes on a grey background with blurred edges; but a closer look reveals that the shapes are made entirely out of lines of text. The text is the philosophical musings of the artist, inspired by Nietzsche.

The lines of text overlap to such an extent that the vast majority of the words cannot be read and complete sentences can never be made out. Viewers are left with tantalising glimpses into the artist's mind with only odd words such as 'desire', 'struggle' and 'form' legible.

It's a nod to the creative process behind abstract art in that the artist's meaning is usually unclear to the viewer and they must make up their own mind as to what the work is telling them. As the colour black is also associated with concealment, for example redacted text, this further heightens the unsettling mystery behind the works' intentions.

The largest piece in the upstairs gallery is being created in situ and so the words are less overlaid, giving greater insight into the creative process but even then only half-sentences can be made out and some mystery still remains.

Granted all these works explore the same concept and they are not hugely different from Khan's previous creations, but the concept itself is well articulated and makes for an engaging exhibition.